P/00/012 Regulation 3.2 AUSTRALIA Patents Act 1990 ORIGINAL COMPLETE SPECIFICATION INNOVATION PATENT Invention Title: "IMPROVEMENTS IN RIGID TONNEAU COVERS" The following statement is a full description of this invention, including the best method of performing it known to me/us: 1 TITLE "IMPROVEMENTS IN RIGID TONNEAU COVERS" FIELD OF THE INVENTION This invention is concerned with rigid shell-like tonneau covers 5 for pickup trucks and the like. The invention is concerned particularly although not exclusively with the manufacture of thermoformed plastics tonneau covers to meet original equipment manufacturer (OEM) standards of motor vehicle manufacturers. 10 BACKGROUND OF THE INVENTION Traditionally, tonneau covers for pickup trucks or utilities have comprised a soft vinyl coated fabric secured about its perimeter to the upper edge of the truck bed by snap/stud combinations or elasticized loops engageable with hooks spaced about the upper edge of the truck bed. 15 Arched support members were located across the truck bed to prevent retention of rainwater by sagging of the soft tonneau cover in the middle thereof. Of more recent times style conscious vehicle owners have replaced the originally supplied soft tonneau cover with a rigid moulded 20 fibreglass cover hingedly mounted to a forward end of the truck bed. Some of these fibreglass covers comprise a relatively thin shell with a decorative coloured gel coat outer surface and a raw glass fibre/resin inner surface. These thin shell covers are inconvenient to handle as they are floppy and prone to damage as they cannot withstand loads. A foam cored fibreglass 25 tonneau cover has a greater load bearing capacity but is significantly heavier 2 and inconvenient to use. Although fibreglass tonneau covers are generally effective for their intended use and able to withstand extremes of weather, they are not regarded as suitable for OEM supply with a new pickup truck as they are 5 expensive, heavy to install and use, prone to chipping and surface cracking in the gel coat layer and otherwise cannot be prepared to inner and outer surface finish levels required by automotive manufacturers, particularly "A" class painted outer surfaces. An alternative to fibreglass tonneau covers is described in 10 United States Patent 6,547,310 which relates to composite structures formed from a thermoplastics sheet such as ABS (Acrylonitrile Butadiene Styrene) polymer. The cover comprises a textured outer layer vacuum formed to a desired shape and an inner support layer comprising a plurality of cruciform support ribs also formed from a single sheet of ABS secured to the outer 15 layer by adhesive bonding. The inner and outer surfaces of the composite structure are formed from ABS sheet embossed with a stipple pattern to disguise surface imperfections. These composite moulded ABS tonneau covers are significantly lighter and less expensive than fibreglass covers. Although generally effective for their intended purpose, the 20 vacuum formed composite ABS tonneau covers of United States Patent 6,547,310 suffer a number of disadvantages which preclude them from compliance with stringent OEM product standards. The main shortcomings relate to the use of a textured outer surface to mask imperfections, the manner in which the outer cover and inner support are bonded giving rise to 25 thermal deformation, the design of the support structure which exacerbates 3 differential thermal expansion between inner and outer members and the configuration of gas strut mounting which causes failure in OEM thermal cycling tests. Thermal cycling tests of vehicle manufacturers are intended to 5 emulate extremes of service conditions and typically products are exposed to repetitive cycles of 26 0 C, 80 0 C, -30 0 C to expose permanent or temporary warping or deformation, although some vehicle manufacturers set an upper temperature limit of 95 0 C for their thermal cycling tests. A typical cycle is illustrated in the following table: CYCLE CYCLE2 SURFACE TEMP TIME SURFACE TEMP TIME 20 0 C 4 HRS 26 0 C 0.5 HRS -20 0 C 1.5 HRS 80 0 C 4 HRS 26 0 C 0.5 HRS -20 0 C 1.5 HRS 80 0 C 3 HRS 26 0 C 0.5 HRS -20 0 C 1.5 HRS 80 0 C 3 HRS -20 0 C 1.5 HRS 10 The coefficient of thermal expansion for ABS polymers is typically in the range 60-130 x 10~8 in/in/C but for some alloys such as a polycarbonate/ABS (PCABS) alloy, this can be in the range of 62-72 x 10-8 in/in/ 0 C. 15 The above tests are required with the tonneau cover fitted to the vehicle body and with all hardware fitted including hinges, gas struts and mounts, locks, etc. One test is carried out with a static 100 Kg load.
4 The tonneau cover of United States Patent 6,547,310 was found to develop an upward deformation at 80 0 C in the region between the hinged mounting at the forward end of the truck body and the pivotal coupling between the gas struts and the tonneau intermediate its forward 5 and rearward ends due to a forwardly directed force applied by the gas struts which were anchored at respective rearward ends to the truck body. Moreover, depressions were formed in a fairly regular manner over the outer surface of the tonneau cover due to differential expansion between the inner and outer skins during thermal cycling. These deformations are believed to 10 arise from the rigid adhesive connection between the inner and outer skins over the entire surface of the recessed portions between the cruciform regions of the inner support member and between the outer edges of the skins. Also, relief from differential thermal stresses is not possible due to the continuous couplings between the diagonal cruciform ribs on the one hand 15 and the transverse/longitudinal cruciform ribs on the other hand which directly couple the corners and the front and rear and side edges respectively. Smaller directly coupled cruciform ribs intersect the diagonal ribs. While the cruciform reinforcement structure of the inner support shell may be sufficient to resist external load forces, it actually works against the 20 composite structure in an unloaded state when subjected to relatively mild thermal cycling conditions to cause patterned dimpling in the top surface of the tonneau cover. In harsh operating conditions, these dimples are likely to become permanent due to a phenomenon in thermoplastic materials known as "cold creep". 25 Accordingly, it is an aim of the present invention to overcome or 5 alleviate at least some of the problems associated with prior art rigid tonneau cover structures and otherwise to provide a cost effective method of manufacture of vacuum formed tonneau covers by a robotic process to produce a product capable of satisfying OEM product standards. 5 SUMMARY OF THE INVENTION According to one aspect of the invention there is provided a thermoformed tonneau cover for a pickup truck or utility, said tonneau cover comprising: a contoured outer shell of thermoformed plastics sheet 10 material; and, a contoured inner shell of thermoplastics material adhesively bonded to said outer shell, said tonneau cover characterized in that said inner shell comprises a reinforcement structure having spaced transverse ribs adjacent respective front and rear ends of said tonneau cover, and 15 spaced longitudinal ribs adjacent respective side edges of said tonneau cover, said transverse ribs and said longitudinal ribs forming a reinforcing array spaced inwardly of outer edges of said inner shell, said inner shell further including a plurality of inner reinforcing ribs connecting with said reinforcing array, each said inner rib being connected at a respective inner 20 end to a recessed member forming a generally centrally located discontinuity, in use, resisting stress transference directly between generally opposed inner ribs. Preferably, respective axes of linear portions of at least some of said generally opposed inner ribs are misaligned. 25 If required, said respective axes of linear portions of at least 6 some of said generally opposed inner ribs are axially aligned. Suitably, said discontinuity comprises a recessed well. If required, said recessed well has a floor structure in contact with an inner surface of said outer shell. 5 Preferably said floor structure is adhesively connected to said inner surface of said outer shell by flexible adhesive compound. The flexible adhesive compound may be formed as a bead extending adjacent a peripheral edge of said floor structure. Suitably, linear reinforcing ribs extend along central transverse 10 and longitudinal axes of said tonneau cover at one end from respective transverse and longitudinal ribs of said array and at an opposite end to said recessed member. If required, recessed regions located on opposite sides of each linear reinforcing rib are adhesively secured to an inner surface of said outer 15 shell by a bead of flexible adhesive compound extending adjacent a peripheral edge of each said recessed region. Preferably, junctions between upper walls of each reinforcing rib and respective side walls thereof and junctions between each said recessed regions and respective rib side walls are radiussed whereby 20 differential thermal expansion and contraction between said outer shell and said inner shell is accommodated at least partially by flexure in said rib side walls. Suitably, differential thermal expansion and contraction between said outer shell and said inner shell is accommodated at least 25 partially by flexible adhesive connections therebetween.
7 If required, said tonneau cover may comprise recessed corner regions on opposite longitudinal edges to accommodate a sports bar or like structure, said tonneau cover comprising complementary infill panels for said recessed corner regions, said infill panels being mountable on a vehicle body 5 to form a flush upper surface therewith. Preferably, said infill panels each include a water run-off channel extending along an inner edge thereof beneath a respective free edge of a recessed corner region. If required, said thermoplastics material is comprised of an ABS 10 polymer or co-polymer. Preferably, said ABS polymer or co-polymer is a polycarbonate/ABS alloy. Suitably, said outer shell comprises ABS with a polymethyl methacrylate outer laminate. 15 Preferably, at least an outer shell of said tonneau is formed from sheet ABS or PCABS having a smooth outer surface to OEM A class paint finish specifications. Suitably, said tonneau cover includes gas strut mounts located rearwardly of gas strut mounts on a vehicle body whereby, in use, restoring 20 forces of gas compressed in said struts are directed rearwardly of forwardly mounted hinge anchors thereby alleviating thermal buckling or distortion in the tonneau cover in the region between the gas strut mounts thereon and the hinge anchor locations. Preferably, said gas strut mounts are located on a side wall or 25 exposed face of said perimeter array.
8 According to another aspect of the invention there is provided a method for the robotic manufacture of thermoformed tonneau covers, said method comprising the steps of: vacuum forming inner and outer shells to predetermined 5 shapes in respective vacuum forming moulds; robotically trimming outer edges of said inner and outer shells to predetermined shapes in respective trimming jigs and forming mounting bracket fastener apertures in said inner shell; attachment, on an inner face of said inner shell with aligned 10 fastener apertures, backing plates for fittings; robotically applying an adhesive composition in a predetermined configuration to selected regions of an inner surface of said inner shell whilst said inner shell is supported in a jig; positioning said outer shell over said inner shell and forming a 15 gas tight seal between respective outer edges of said inner shell and said outer shell and reducing the air pressure between said inner and outer shell for a predetermined period to allow at least partial curing of said adhesive composition; conveying a so assembled tonneau cover to a robotic trimming 20 station to trim an outer edge of said assembly to a predetermined dimensional configuration; conveying said assembly to a paint station and robotically painting an outer surface of said assembly to an OEM specified finish level. If required, said inner and outer shells may be formed with 25 removable complementary corner inserts separable from said inner and 9 outer shells during robotic trimming of the outer edges thereof. Suitably, support jigs for robotic trimming, adhesive application, assembly and/or painting of tonneau covers having corner infill panels are adapted to support said infill panels for processing with respective said inner 5 and outer shells and said assembly. BRIEF DESCRIPTION OF THE INVENTION In order that the various aspects of the invention may be more fully understood and put into practical effect, reference will now be made to preferred embodiments illustrated in the accompanying drawings in which: 10 FIG. 1 shows an exploded upper view of a thermoformed tonneau cover with corner infill panels; FIG. 2 shows an inverted view of the exploded assembly of FIG. 1; FIG. 3 shows an assembled view of the tonneau cover of FIG. 15 1 from above; FIG. 4 shows a cross-sectional view of the tonneau assembly through A-A in FIG. 3; FIG. 5 shows a cross-sectional view of the tonneau assembly through B-B in FIG. 3; and 20 FIG. 6 shows an enlarged partial cross-sectional view of the region encircled in FIG. 5. In the drawings like reference numerals are employed for like features for the sake of simplicity. DETAILED DESCRIPTION OF THE DRAWINGS 25 The preferred embodiment described herein relates to a 10 tonneau cover with separate infill panels to accommodate sports bars or the like attached to a vehicle. It should be understood that the invention is not so limited and refers to tonneau covers without infill panels. In FIG. 1, tonneau cover 1 comprises an outer shell portion 2 5 and separate corner infill panels 3 which accommodate a sports bar fitted to a pickup truck body or the back of a utility. Each of outer shell portion 2 and infill panel 3 are thermoformed by a vacuum moulding process from ABS or PCABS sheet as required having an "A" grade surface finish free from blemishes and imperfections. Outer shell portion 2 has a smooth compound 10 curvature over longitudinal and transverse axes A and B respectively and the side and rear edges 4,5 each are formed with a smooth radiussed curve. Rear edge 5 has a shaped cut out portion 6 to accommodate a latch mechanism in the tailgate of the vehicle. Corner infill panels 3 as shown are adapted to be located 15 between a sports bar (not shown) and mounting brackets (not shown) on the vehicle body (also not shown) and are secured in that position by threaded shanks extending from the mounting bases of the sports bar via apertures 7 through aligned apertures in the mounting brackets on the vehicle. Infill panels 3 include drainage channels 8 to collect water from an overlapping 20 recessed side edge 9 of outer shell portion 2 when in use. FIG. 2 shows an inverted view of the assembly of FIG. 1 illustrating inner shell portions 2a and 3a of tonneau cover 1 and infill panels 3 respectively. Inner shell portions 2a and 3a are vacuum formed from ABS sheet having an embossed stipple pattern or the like and are adhesively 25 bonded to respective outer shell portions. Inner shell portion 2a is bonded to 11 outer shell 2 by a cross linkable flexible acrylate-based adhesive applied as a bead to bead support lands 10 extending about the periphery of recessed regions 11 and also about an inner peripheral edge 12 of the entire inner shell 2. Bead support lands 10 are formed as slightly raised rib-like 5 formations on the surface abutting an inner surface of outer shell 2 to ensure a good localized compression of the adhesive bead during assembly of the inner and outer shells 2a,2. Infill panels simply have a bead of adhesive between the inner and outer shells 3a,3 between localized rib features and about the peripheral edges thereof. 10 The inner region of inner shell 2 is formed as a deeply drawn array of ribs comprising a rectangular perimeter array 13 comprising a spaced pair of longitudinal ribs 14 and a spaced pair of transverse ribs 15. Extending between adjacent transverse corners and adjacent longitudinal corners is an arcuate rib structure 16 formed as a blend of a pair of arcuate 15 ribs 17 extending between adjacent transverse corners of perimeter array 13 and a pair of arcuate ribs 18 extending between adjacent longitudinal corners 19 whereby each adjacent pair of arcuate ribs 17,18 shares a common leg portion 17a,18a. The region between the respective adjacent zeniths of arcuate 20 ribs 17,18 is formed as a recess 19 with a floor 20 also adhered to outer shell 2 by an adhesive bead positioned on a support land about the perimeter of recess 19. It will be noted that the respective central axes 21 of common leg portions interact at locii spaced from a geometric central axis at the intersection of diagonals of perimeter array 13. 25 For example, the axes 21 of legs 17a intersect on respective 12 near sides of recess 19 while the axes 21 of legs 18a intersect on respective far sides of recess 19. Accordingly, when a temperature gradient exists between the outer shell 2 and inner shell 3, forces imposed on the reinforcing rib structure formed in inner shell 3 by relative expansion or 5 contraction between the inner and outer shells are evenly distributed through the interconnecting arcuate ribs 17,18 rather than directly between opposing edges and corners as would otherwise occur with an unyielding cruciform structure. Additional ribs 22,23 extend between respective ribs 14 and 15 10 perpendicular thereto to the respective inner side walls of the actuate ribs 17,18 along transverse axis A-A and longitudinal axis B-B respectively. Importantly, it will be noted that each of the intersections formed between the upper surfaces of arcuate rib legs 17a,18a and respective corners of perimeter rib array 13 are formed as radiussed steps 24. Similarly, the 15 opposite ends of each rib 22,23 connect at their upper surfaces with respective upper surfaces of ribs 14, 15,17 and 18 also as radiussed steps 24. Moreover, the side walls of all ribs 14, 15, 17 and 18 form radiussed rib junctions 24a with recessed floors of recessed regions 11 and respective upper rib surfaces. Each of these radiussed junctions 24a effectively forms a 20 hinged connection between recessed regions 11 adjacent the outer skin 2 and the upper surfaces of ribs 14, 15, 17 and 18. Moreover, by employing a cross-linking somewhat flexible adhesive to bond the inner and outer shells 2,2a respectively, a further degree of stress relief is obtained due to relative expansion and contraction 25 between the inner and outer shells due to temperature gradients 13 therebetween. The perimetral region 25 of the tonneau cover 1 is formed with an additional shallower reinforcing rib 26 which corresponds with the upper edge of the vehicle body and as such, serves as a convenient surface 27 to 5 adhesively mount a polyethylene foam weather sealing tape (not shown). Additional spaced shallow ribs 28 formed between the perimeter rib array 13 and outer reinforcing rib 26 not only reinforce the edge region of the tonneau cover but also provide convenient mounting points for "hardware" attached to the inside of the tonneau cover as backing support plates are easily located 10 in the recesses formed thereby between the inner and outer skins. For example, the mountings for gas struts may be located in ribs 14 as shown at 30 while tonneau cover hinges may be mounted on ribs 28b. Alternatively, the gas struts may be mounted to an upright side wall of ribs 14. Corner infill panels 3 similarly include an outer rib 29 15 corresponding to outer rib 26 of cover 1 and, similarly, provide a mounting surface for the polyethylene foam weather sealing strip. Small transverse ribs 30 in inner shell 3a provide additional reinforcement to panels 3. FIG. 3 shows the juxtaposition of tonneau cover 1 and corner infill panels as they would appear when mounted on a vehicle body. As can 20 be seen, the free edge 9 of the forward side regions 31 overlaps the drainage channel 8 as shown in FIG. 1. FIG. 4 shows a longitudinal cross-section through A-A in FIG. 3 wherein the radiussed rib junctions and radiussed steps 24 and their capacity to absorb compression and tension in the ribs is more clearly shown. 25 FIG. 5 shows a transverse cross-section through B-B in FIG. 3 14 wherein again the radiussed rib junctions and radiussed steps 24 and their capacity to absorb compressive and tensile forces due to differential thermal expansion and contraction between the inner and outer skins is more clearly shown. 5 In addition, adhesive bead support lands can be seen between the adjacent surfaces of the inner and outer shells. FIG. 6 shows an enlarged cross-sectional view of the region encircled in FIG. 5. In FIG. 6, the juxtaposition of the infill panel 3 relative to the 10 recessed edge 9 is such that any water running over the outer surface of outer skin 2 collects in drainage channel 8 and flows outwardly to the outer edge of infill panel 3 where it overhangs the edge of the vehicle body. A resilient strip of polyethylene foam 35 is adhered to an under surface of inner shell 2a such that when tonneau cover 1 is in a closed 15 position as represented in FIG. 6, a watertight seal is effected between the inner shell 2a and the inner edge of drainage channel 8. In the manufacture of tonneau covers according to the invention, it has been found that manual trim, adhesive application, assembly, final trim and painting processes could not meet the rigid OEM 20 requirements for consistency in close tolerances for dimensions, structural integrity and final surface finish. Accordingly, a method of automating the various process steps was devised whereby these rigid OEM standards could be met and maintained. Moreover, to accommodate a choice of tonneau covers adapted for or without sports bar fittings on the vehicle, 25 modular moulds and jigs were devised to avoid the high capital costs of a 15 plurality of differing moulds and jigs for tonneau covers with and without sports bar infill panels were also devised. Importantly, during all stages of the manufacturing process through to final paint finishing, the separate inner and outer shells of the infill panels, which are formed simultaneously with 5 respective inner and outer tonneau cover shells, accompanying the tonneau through all stages of treatment to avoid any inconsistency in dimensions assembly or finish between the tonneau cover and the infill panels. In the manufacturing process, pre-cut sheets of ABS for the inner and outer tonneau shells are fed into an automated vacuum forming 10 apparatus having alternating paired inner and outer shell moulds fortonneau covers with or without infill panels. Moulded pairs of shells, some with attached infill panel shells are then conveyed to a trimming station where the outer edges are trimmed in respective jigs by a robotic trimmer operating a high speed router blade or the like. Where the inner and outer shells 15 incorporate an integrally formed inner and outer infill panel, these too are separated and trimmed in respective trimming jigs by the robotic trimmer. After the trimming process, the inner shell in a support jig has holes drilled for mounting of tonneau hardware such as hinges, gas strut mounts, locking mechanisms and the like and mounting plates are located on an inner 20 surface with aligned mounting apertures. A pair of trimmed inner and outer tonneau shells, with respective inner and outer infill panel shells is conveyed to an adhesive station and the inner tonneau shells and respective inner infill panel shells is located in an adhesive jig with inner surfaces uppermost. A robotic adhesive 25 applicator applies a two component cross-linkable partially flexible adhesive 16 to the inner surface of the inner shell. By inner surface it is meant that surface which abuts an inner surface of an outer shell when assembled. The adhesive is applied as a pattern of bead-like depositions to selected regions of the inner shell on the adhesive lands 10 as shown in FIGS. 2 and 5 and 5 also about the peripheral edges. The outer shells of the tonneau cover and infill panels are then guided into location with the respective inner panels and a vacuum is applied to the air gap between the inner and outer shells, via the mounting holes in the inner shell, by a vacuum pump coupled to a plenum under the mounting jig. 10 The assembly is then subjected to elevated temperature for a predetermined period to accelerate the cross-linking of the adhesive. After the adhesive has cured, the assembly of inner and outer shells together with respective assembled infill panels is then allowed to cool before being conveyed to a robotic painting station where a paint finish is applied 15 robotically to match the paint hue and finish of a newly manufactured vehicle. The finished tonneaus and infill panels are then packed for despatch. It readily will be apparent that many modifications and variations may be made to the various aspects of the invention without department from the spirit and scope thereof. 20 For example, certain manufacturers require thermal cycling tests to be performed between the ranges -20'C to 95'C. to withstand buckling or deformation in a static 100 Kg load test, a polycarbonate/ABS alloy is preferred at least for the outer shell material as it has a greater softening temperature. The combination of at least a PCABS outer shell in 25 combination with a gas strut mounting system which places the tonneau 17 cover in tension during the thermal cycling process is found to avoid the buckling as otherwise encountered in prior art thermoformed ABS tonneaus which have a gas strut mounting arrangement which places the tonneau in compression between the hinge mounting and the gas strut mounting on the 5 tonneau cover. It equally will be readily apparent to persons skilled in the art that the present invention may be adapted for aftermarket sales where the requirement for high quality OEM A class paint finishes is not as great. In these aftermarket applications, an ABS or PCABS sheet having a less than 10 A class finish may be employed or the sheet may have an embossed textured finish to ask imperfections arising from the use of regrind materials in the manufacture of the sheet.